Dynamic control approach for motion coordination of multiple wheeled mobile robots transporting a single object

This paper proposes a coordinate dynamic control method for the transfer of a common heavy object by several wheeled mobile robots. The coupler, which comprises an active prismatic link and a passive rotary joint, is installed on each robot so that even an ordinary nonholomonic mobile robot with inferior mobility can correctly manipulate the object. A hierarchical coordinative control system composed of a leader and other staff robots is designed to synchronously control the motions of the robots under severe dynamic interactions. The leader robot successively defines the desired motion of the object along its reference trajectory and broadcasts the information to the staff robots. Each staff robot controls the motions of its own body and the onboard prismatic link so as to achieve the desired object behavior without sideways slippages. When the prismatic link approaches the limit for its movement, the staff robot requests the leader to temporarily modify the desired behavior of the object. The control algorithm is formulated on the basis of the kinematics and the dynamics of the wheeled mobile robot. Simulation results illustrate the validity of the method